Emmanuel Steven Emelogu
Combined effects of bioavailable organic contaminants in the aquatic environment.
Emelogu, Emmanuel Steven
In contrast to conventional spot or bottle water sampling techniques, passive sampling has been shown to be a reliable and efficient method for monitoring the toxicologically-relevant, freely-dissolved (e.g. bioavaialable) concentrations of a wide range of organic contaminants in water. At the same time, techniques for partitioning controlled delivery (passive dosing; PD) promise to overcome many of the challenges associated with toxicity testing of hydrophobic substances, which can bias the interpretation of toxicity data. The present study investigated the feasibility of coupling silicone rubber passive sampling devices (SR-PSDs) with bioassay techniques for both chemical and ecotoxicological assessment of complex mixtures of organic contaminants in the aquatic environment. SR-PSDs were deployed for seven to nine weeks in water at various locations within the Ythan catchment (north-east of Scotland), and within the Forth estuary and the Firth of Forth (east coast of central Scotland). Following retrieval, extracts from the SR-PSDs were analysed for dissolved concentrations of a variety of organic contaminants, including PAHs (using GC-MS) and PCBs (using GC-ECD). They were then screened for a wide range of pesticides using GC-MS/MS and LC-MS/MS. The extracts were further evaluated for acute cytotoxicity (i.e. neutral red uptake assay) and EROD induction potential using rainbow trout liver cell line (Oncorhynchus mykiss; RTL-W1). They were also evaluated for phytotoxicity and developmental toxicity potential, using an algal growth inhibition test with a marine phytoplankton (Diacronema lutheri) and a fish embryo toxicity test with embryos from zebrafish (Danio rerio) respectively. Overall, the individual and total dissolved concentrations of PAHs (Sigma-PAH40; parent and branched) and PCBs (Sigma-PCB32; ortho and mono-ortho) measured in water from the Ythan, Forth estuary and Firth of Forth were relatively low compared with other studies using PSDs. A number and level of pesticides, including insecticides, herbicides and fungicides of varying hydrophobicity (log KOWs ~2.25 to ~5.31) were detected in the silicone rubber (SR) extracts from all three areas, suggesting input mainly from agricultural run-off and possibly from direct discharges. No statistically significant (p < 0.05) acute cytotoxicity was observed following forty-eight hours of exposure of RTL-W1 cells to SR extracts from the Ythan catchment. However, on a sublethal level for every site, statistically significant EROD activity was observed to some degree following seventy-two hours of exposure. In addition, developmental and algal toxicities on embryos of D. rerio and D. lutheri were measured in all the deployed samples compared with the procedural controls (undeployed samples). Interestingly, extracts of SR-PSDs from the Forth estuary and the Firth of Forth exhibited growth inhibitions on D. lutheri that were similar to those of extracts from the Ythan, even though fewer pesticides were detected in the Forth estuary and Firth of Forth than the Ythan. This suggests that pesticides were not solely responsible for the observed effects in the Ythan catchment. To further improve data from toxicity testing of hydrophobic substances, the study identified the use of SR O-rings as a suitable passive dosing format in toxicity tests in vitro, and was partially validated through their use in dosing RTL-W1 cells with two individual PAHs, which subsequently determined both cytotoxicity and EROD-activity.
EMELOGU, E.S. 2013. Combined effects of bioavailable organic contaminants in the aquatic environment. Robert Gordon University, PhD thesis.
|Deposit Date||Jul 30, 2013|
|Publicly Available Date||Jul 30, 2013|
|Keywords||Silicone rubber passive sampling (SRPS); Passive dosing; Hydrophobic organic contaminants (HOCs); Fish embryotoxicity test (FET); Bioassays; Bioavailable; Water quality monitoring; Toxicity testing; Pesticides; Algal growth inhibition (AGI)|
EMELOGU 2013 Combined effects of bioavailable
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Copyright: the author and Robert Gordon University